Many portable electronic devices include switching power supplies (e.g., DC-to-DC converters) having a circuit topology (e.g., flyback, buck, boost, push-pull, etc.) with one or more large passive components (e.g., an inductor). The switching power supply circuits can be bulky and may consume a large volume of current. Switching power supplies can also be inefficient, particularly if, for example, a cascade of DC-to-DC converters is used generate voltages on multiple rails. Moreover, switching power supplies can generate electro-magnetic interference and switching harmonics, which can produce noise in an image (e.g., an ultrasound image) formed by a system connected to the power supply. Mitigation of the noise sources may require using extensive countermeasures such as, for example, synchronization of the switching supplies to the acquisition timing (e.g., with a Doppler image) and/or extensive passive filtering and shielding (e.g., with a B-Mode image). Given these problems and others, a need exists for a simpler, more efficient circuit configuration that produces various voltage levels with minimal noise.